We present a 10-week-old girl with myositis ossificans circumscripta (MO) of the neck secondary to nonaccidental trauma. This condition is rarely seen in infants; furthermore, the majority of MO lesions develop in the extremities rather than the head and neck region. We will detail the US-guided biopsy technique used in our case, in addition to discussing the characteristic imaging and pathological findings of MO to assist in the diagnosis and successful treatment of this condition.